I did ear deployment in weblogic 10.It conatins war, ejb jar, APP-INF, META-INF. Now When I am calling the service from war, I am getting classnot found exception.When I deploy the war file , without using ear file this service works absoulutely fine.
How to resolve this problem. How classloader will check for jars
It's impossible to solve your problem without more details but as you asked for documentation on how classloaders work in WebLogic, you will find information in Understanding WebLogic Server Application Classloading. Also have a look at Understanding J2EE Application Server Class Loading Architectures on TheServerSide.com (quite old but still perfectly valid).
In your particular case, I'd like to know if you are using Manifest Class-Path entries. More details on how your EAR is structure exactly would be also welcome. Please update your question accordingly.